As is known, a CT scanning system uses ionizing radiation (X-rays) to generate images of tissues, organs, and other structures within a body. The X-ray data resulting from a CT scan may be converted into images on a computer display screen. For example, the CT scan provides a collection of data used to create a three dimensional (3D) volume corresponding to the scanned portion of a patient's body. The 3D volume is then sliced to create images of body tissue at small intervals along an axis of the patient's body. Such slices may include both lateral and transverse slices (as well as other slices) depending on the tissues or structures being imaged.
The use of CT scans and ionizing radiation for medical imaging has grown exponentially over the past decade. And modern techniques such as CT scanning provide much more detailed and valuable diagnostic information than conventional X-ray imaging. Concurrently however, patients are being exposed to substantially larger doses of radiation. For example, a typical chest CT will expose a patient to anywhere between 100-250 times the dose of a conventional chest X-Ray depending on the voltage and current of the CT scanning system, the protocol followed to perform the procedure, and the size and shape of the patient being scanned.
Despite the increased use of CT scans (and resulting exposure to radiation) the amount of radiation a patient is exposed to during a procedure, and importantly, the cumulative dose over many procedures are not parameters are regularly tracked for a patient, and nor are these parameters readily accessible part of the patient's medical records. This occurs in part because the amount of radiation absorbed by internal organs and tissues cannot be measured in live patients directly as part of a CT exam, and results obtained from cadavers, while more accurate, do not correspond well to dose absorption in live tissues.
Similarly, approaches for estimating dose used currently also provide inaccurate results. For example, one approach is to rely on a limited number of physical imaging phantoms to represent a given patient. However, the available imaging phantoms do not adequately represent the broad variation in people's size and weight in the population of individuals receiving CT scans. As a result, single point surface measurements are what is currently done in the majority of cases where dose is estimated at all. However, this leads to both poor and widely varying results, depending on where the single point dose is measured. More generally, surface measurements of radiation exposure do not provide an accurate measure of actual absorption for internal tissues, organs, and structures.